1. Field of the Invention
The invention relates to the field of controllers for interfacing between a digital computer and a floppy disk drive. The disclosed invention is particularly suited for implementation as an integrated circuit.
2. Prior Art
Floppy disk controllers for interfacing between digital computers and floppy disk drives are well known. Such disk drives include a motor for rotating a floppy disk, a floppy disk being comprised of a flexible material shaped such that it is flat and circular and onto which is bonded a magnetic medium; a write head for recording data on the magnetic medium and a read head for reading data from the magnetic medium; a stepper motor for moving the read and write heads along the surface of the floppy disk; and electronic and logic circuitry for receiving binary signals which turn the disk drive motor on and off, move the read and write heads and cause electrical signals to be sent to the write head for recording data or receive electrical signals generated by the read head as the magnetic medium rotates past it. Disk drive controllers generate the necessary binary signals to turn the disk drive motor on and off, move the read and write heads and send appropriate signals to the electronic and logic circuitry of the disk drive to cause the read and write heads to read from or write to the magnetic medium of the rotating floppy disk. Disk drive controllers generate the appropriate signals to control the operation of disk drives by appropriate control, data and clock signals received from a digital computer.
In U.S. Pat. No. 4,210,959, a floppy disk drive controller is disclosed comprised of a serial/parallel shift register, controller logic and timing means and latches. The serial/parallel shift register is used to transfer data to and from the computer on a data bus. The controller logic and timing means receives signals from the latches to place the controller logic means in one of four possible modes of operation namely, read, sense write protect/write initialize, write record and write load. All reading and writing is done in a synchronous manner based upon a clock signal CLK. The aforesaid invention is directed to a relatively simple, inexpensive controller suitable for consumer and small business applications. The present invention is an integration of the controller disclosed in U.S. Pat. No. 4,210,959 with extensions and improvements including the capability of multiple modes of operation.